Charge cooling circuit for a multi-cylinder internal combustion engine with a turbo-supercharger

ABSTRACT

In the case of a charge-air cooling circuit for a multicylinder internal-combustion engine  1  with a turbo-supercharger  2,  it is proposed that downstream from the turbo-supercharger  2  the charge air be fed to two separate charge-air coolers  6, 6′,  whereby the first charge-air cooler  6  divides the charge air into two flow branches I, II, effectively cools the first of the two flow branches I, and allows the second of the two flow branches II to pass essentially uncooled, and whereby the second charge-air cooler  6′  allows the first of the two flow-branches I to pass essentially uncooled, effectively cools the second of the two flow branches II, and then recombines the two flow branches I, II. According to the proposal, it is ensured that this charge-air cooling circuit is adapted to the special spatial conditions that exist inside the engine compartment of a multi-cylinder internal-combustion engine, especially an internal-combustion engine of the V-design, and provides for improved cooling performance compared to the state of the art.

DESCRIPTION

[0001] The present invention relates to a charge cooling circuit for amulti-cylinder internal-combustion engine with a turbo-supercharger.

[0002] From document DE 31 04 124 A1 a charge-air cooler for a vehiclewith a supercharged internal-combustion engine is known, whereby inorder to reduce the size of the charge-air cooler a bypass that has avalve arrangement and that blocks the bypass in a low rpm range of theinternal-combustion engine is provided.

[0003] Moreover, document DE 31 04 072 C1 describes a process foraccelerating the warming-up of an engine in which, depending on thecooling-water temperature and the temperature of the charge air, thecharge air is directed to the internal-combustion engine either througha charge-air cooler or through a bypass.

[0004] If high charge-air temperatures prevail, however, with thecharge-air cooling circuits disclosed in these documents there is theproblem that the surface area of the charge-air cooler has to be aslarge as possible in order to ensure adequate cooling, but it is verydifficult to accomplish this because of the cramped conditions thatprevail in the engine compartment.

[0005] Finally, from document DE 195 47 994 A1 a V-designinternal-combustion engine with two exhaust-gas turbo-superchargers thatoperate in parallel is known, whereby from each of the two exhaust-gasturbo-superchargers a feed line runs to one of two charge-air coolersthat are arranged next to each other and whereby from each of the twocharge-air coolers a return line runs to an intake system. To create aswitchable bypass, provisions are made to ensure that in each case thefeed line of the one charge-air cooler is connected to the return lineof the other charge-air cooler and that this connection is equipped witha switchable bypass valve.

[0006] In all the charge-air cooling circuits described by theabove-mentioned documents, there is also the problem that the coolingresults that can be achieved are not entirely satisfactory.

[0007] Taking this state of the art as a point of departure, the objectof the present intention is to design a charge-air cooling circuit for amulti-cylinder internal-combustion engine with a turbo-superchargerwhereby said the charge-air cooling circuit can be readily accommodatedin the engine compartment and whereby said charge-air cooling circuitprovides better cooling performance than that offered by the state ofthe art.

[0008] This object is achieved by virtue of the fact that downstreamfrom the turbo-supercharger the charge air is fed to two separatecharge-air coolers, whereby the first charge-air cooler divides thecharge air into two flow branches, effectively cools the first of thetwo flow branches, and allows the second of the two flow branches topass essentially uncooled, and whereby the second charge-air coolerallows the first of the two flow branches to pass essentially uncooled,effectively cools the second of the two flow branches, and thenrecombines the two flow branches.

[0009] This makes it possible to have two smaller charge-air coolersrather than one large charge-air cooler and to arrange for these twocharge-air coolers to be largely independent of one another, such thatthey occupy favorable locations in the engine compartment and do notinterfere with one another. Moreover, the charge air, which is splitinto two flow branches, can be cooled more effectively because, asexperiments with the charge-air cooling circuit according to theinvention have shown, the cooling of the two flow branches, which takesplace in different sequences and at different locations, turns out to beespecially effective.

[0010] According to the invention, the first charge-air cooler has aninlet for the charge air to which one air receiver with a branchingpoint is connected, whereby the first flow branch is directed to thebranching point through a cool pass, the second flow branch is directedto the branching point through a bypass, and the two flow branches arethen directed to two separate outlets of the cool pass and the bypass.

[0011] Moreover, the second charge-air cooler according to the inventionhas two separate inlets for the two flow branches to which a bypass anda cool pass are connected, whereby the first flow branch is directedthrough the bypass, the second flow branch is directed through the coolpass, the two flow branches are then directed inside the air receiver toa combining point, and an outlet for the charge air is connected to thecombining point.

[0012] It is advantageous for the first charge-air cooler and the secondcharge-air cooler to be designed to be mirror-symmetric. The reason isthat in this way the two charge-air coolers can be produced in acost-effective manner.

[0013] It is advisable for the two flow branches to have the samequantities of charge air in order to ensure that the two flow brancheshave approximately the same temperature in the area of the combiningpoint so that the charge air that is fed to the intake system of theinternal-combustion engine has a largely homogeneous temperaturedistribution.

[0014] It is likewise advisable for both of the two flow branches to beof approximately the same length from the branching point inside the airreceiver of the first charge-air cooler to the combining point insidethe air receiver of the second charge-air cooler. This makes it simplerto design the two flow branches alike.

[0015] Of course, the branching point inside the air receiver of thefirst charge-air cooler and/or the combining point inside the airreceiver of the second charge-air cooler can also be equipped with acontrollable element so that the output of the charge-air coolingcircuit can be reduced during the cold-start phase of theinternal-combustion engine. The reason for this is that the controllableelement makes it possible to direct the charge air to the intake systemof the internal-combustion engine in an essentially uncooled state,i.e., through the bypasses only, and to bring about effective cooling ofthe charge air only after a certain temperature is reached.

[0016] The two flow branches that extend between the two charge-aircoolers are preferably designed at least partially as a rigid doubletube, whereby the two charge-air coolers and the rigid double tube areeach connected together by means of flexible delivery hoses. With thisapproach, the charge air can be directed even over a relatively longdistance inside the engine compartment, thereby avoiding the use of longsuspended and thus easily damaged delivery hoses.

[0017] In a special embodiment, the two charge-air coolers are arrangedon either side of the multi-cylinder internal-combustion engine in theengine compartment, i.e., at positions that are favorable for flow.Moreover, if in both charge-air coolers the cool pass is arranged on theside facing the internal-combustion engine while the bypass is arrangedon the side of the internal-combustion engine facing away from theengine, then this arrangement is also especially appropriate in caseswhere the charge-air coolers are to be installed in a V-design in amulticylinder internal-combustion engine.

[0018] If in addition the second charge-air cooler has a pressure sensorin the area of the air receiver, then by monitoring the pressureprevailing there and, optionally, controlling the turbo-supercharger itis possible to set a charge pressure that is optimal for the runningstate of the internal-combustion engine.

[0019] This invention is explained in greater detail by referring to thefollowing drawing FIGURE:

[0020] The FIGURE shows the charge-air cooling circuit according to theinvention for a multicylinder internal-combustion engine with aturbo-supercharger.

[0021] In the case of a multi-cylinder internal-combustion engine 1whose cylinders are arranged in a V design with respect to one another,the exhaust gas is directed through a turbo-supercharger 2 to an exhaustgas system 3.

[0022] The turbo-supercharger 2 that is driven in this way compresses toa certain charge pressure the fresh air that is taken in by way of adownstream air filter 4, thereby raising the temperature of the chargeair.

[0023] Before the hot charge air can be fed to the intake system 5 ofthe internal-combustion engine 1, it is cooled by means of the firstcharge-air cooler 6 and by means of a second charge-air cooler 6′. Thisis done by ensuring that all of the charge air is initially fed to thefirst charge-air cooler 6 in whose air receiver 7 a branching point 8 islocated where the charge air is split into two flow branches I, II,whereby the first flow branch I is directed through a cool pass 9located inside the first charge-air cooler 6, while the second flowbranch II is directed through a bypass 10 located inside the firstcharge-air cooler 6. Then the two flow branches I, II exit the firstcharge-air cooler 6 and are directed through separate lines 11, 12 tothe second charge-air cooler 6′. These lines 11, 12 can be formed atleast partially by a rigid double tube, thereby increasing themechanical strength of the arrangement. In the second charge-air cooler6′, and the first flow branch I is directed through a bypass 10′, whilethe second flow branch II is directed through a cool pass 9′. Downstreamfrom the bypass 10′ and the cool pass 9′, the two flow branches I, IIare fed to the air receiver 7′ of the second charge-air cooler 6′ byvirtue of the fact that a combining point 13 is provided for the twoflow branches I, II. Behind the second charge-air cooler 6 ′, all of thecharge air is fed through the intake system 5 of the internal-combustionengine 1.

[0024] The first and second charge-air coolers 6, 6′ are arranged oneither side of the internal-combustion engine 1 since this arrangementis especially favorable for flow and, despite the cramped conditionsthat exist in the engine compartment, said arrangement allows arelatively large cooling surface area. The two cool passes 9, 9′ areboth located on the sides of the charge-air coolers 6, 6′ that face theinternal-combustion engine 1, and the two bypasses 10, 10′ are botharranged on the sides of the charge-air coolers 6, 6′ facing away fromthe internal-combustion engine 1.

1. A charge-air cooling circuit for a multi-cylinder internal-combustionengine with a turbo-supercharger, characterized by the fact thatdownstream from the turbo-supercharger (2) the charge air is fed to twoseparate charge-air coolers (6, 6′), whereby the first charge-air cooler(6) divides the charge air into two flow branches (I, II), effectivelycools the first of the two flow branches (I), and allows the second ofthe flow branches (II) to pass essentially uncooled, and whereby thesecond charge-air cooler (6′) allows the first of the two flow branches(I) to pass essentially uncooled, effectively cools the second of thetwo flow branches (II), and recombines the two flow branches (I, II). 2.The charge-air cooling circuit as claimed in, claim 1, wherein the firstcharge-air cooler (6) has an inlet for the charge air to which an airreceiver (7) with a branching point (8) is connected, whereby the firstflow branch (I) is directed to the branching point (8) through a coolpass (9), the second flow branch (II) is directed to the branching point(8) through a bypass (10), and the two flow branches (I, II) are thendirected to two separate outlets of the cool pass (9) and the bypass(10).
 3. The charge-air cooling circuit as claimed in claim 1 or 2,wherein the second charge-air cooler (6′) has two separate inlets forthe two flow branches (I, II) to which a bypass (10′) and a cool pass(9′) are connected, whereby the first flow branch (I) is directedthrough the bypass (10′), the second flow branch (II) is directedthrough the cool pass (9′), the two flow branches (I, II) are thendirected to an air receiver (7′) with a combining point (13), and anoutlet for the charge air is connected to the combining point (13). 4.The charge-air cooling circuit as claimed in one of claims 1-3, whereinthe first charge-air cooler (6) and the second charge-air cooler (6′)are designed to be mirror-symmetric with respect to one another.
 5. Thecharge-air cooling circuit as claimed in one of claims 1-4, wherein thetwo flow branches (I, II) carry equal quantities of charge air.
 6. Thecharge-air cooling circuit as claimed in one of claims 2-5, wherein fromthe branching point (8) inside the air receiver (7) of the firstcharge-air cooler (6) to the combining point (13) inside the airreceiver (7′) of the second charge-air cooler (6′) the two flow branches(I, II) are of approximately equal length.
 7. The charge-air coolingcircuit as claimed in one of claims 2-6, wherein the branching point (8)inside the air receiver (7) of the first charge-air cooler (6) and/orthe combining point (13) inside the air receiver (7′) of the secondcharge-air cooler (6′) are equipped with a controllable element.
 8. Thecharge-air cooling circuit as claimed in one of claims 1-7, wherein thetwo flow branches (I, II) that extend between the two charge-air coolers(6, 6′) are designed at least partially as a rigid double tube, wherebythe two charge-air coolers (6, 6′) and the rigid double tube are eachconnected together by means of flexible delivery hoses.
 9. Thecharge-air cooling circuit as claimed in one of claims 1-8, wherein thetwo charge-air coolers (6, 6′) are arranged in the engine compartment oneither side of the multi-cylinder internal-combustion engine (1). 10.The charge-air cooling circuit as claimed in one of claims 1-9; whereinin the case of both the charge-air coolers (6, 6′) the cool pass (9, 9′)is located on the side facing the internal-combustion engine (1) and thebypass (10, 10′) is arranged on the side facing away from theinternal-combustion engine (1).
 11. The charge-air cooling circuit asclaimed in one of claims 3-10, wherein the second charge-air cooler (6′)has a pressure sensor in the area of the air receiver (7′).